An Advanced Super Dimension Switching (ADS) liquid crystal display (LCD) is used to increase light transmittance of the LCD device across a plane. A multi-dimensional electric field is formed with both an electric field produced at edges of slit electrodes in the same plane and an electric field produced between a slit electrode layer and a plate-like electrode layer, so that liquid crystal molecules at all orientations, which are located directly above the electrodes and between the slit electrodes in a liquid crystal cell, can be rotated, which enhances the work efficiency of liquid crystals and increases the light transmittance. The Advanced Super Dimensional Switching technology can improve the picture quality of thin film transistor liquid crystal displays (TFT-LCDs) and has advantages of high transmittance, wide viewing angle, high aperture ratio, low chromatic aberration, being free of push Mura, etc.
Specific explanations are provided as follows. A LCD of ADS mode comprises an array substrate, a color filter substrate, and a liquid crystal layer interposed therebetween. Each pixel region is defined on an array substrate by a gate line and a data line which are formed to intersect with each other, and a switching device is disposed at an intersection of the gate line and the data line. The pixel region comprises a first transparent electrode and a second transparent electrode, wherein the second transparent electrode is a slit-like electrode, and the first transparent electrode and the second transparent electrode are separated from each other by an insulating layer. The first transparent electrode together with the second transparent electrode produces an electrical field that effects on liquid crystal molecules in a liquid crystal layer, thereby controlling the light transparency and forming a high-quality picture.
The electrical field for smoothly acting on the liquid crystal molecules in the liquid crystal layer is suitably generated at a boundary region between a slit and an elongated strip of the second transparent electrode by the LCD of ADS mode. Upon being etched, the strip of the second transparent electrode requires to approximately keep at a standard value of 4 μm, so that the light transmittance can be well controlled, and undesired visual effects, such as pictures with over-brightness, too large chromatic aberration, and etc., can be avoided as much as possible.
Currently, the slit and the elongated strip in the second transparent electrode can be obtained by a patterning process on the second transparent electrode, which is specifically as follows:
1) forming a layer of transparent electrode film on an array substrate;
2) applying photoresist on the transparent electrode film;
3) disposing a mask plate (comprising a light-transmitting portion and a light-blocking portion) over the substrate obtained in the step 2) and exposing, so that a portion of the photoresist is irradiated and denaturized;
4) developing the substrate, and then removing the portion of the photoresist;
5) etching the substrate, and then removing the portion of the transparent electrode film not being protected by the photoresist, thus a pattern is achieved. In an example of using positive photoresist, the portion of the photoresist which is irradiated by the light is denaturized and removed during the developing; the transparent electrode film under the photoresist not being irradiated is not etched so as to remain. Therefore, as for the second transparent electrode, the slit corresponds to the light-transmitting portion of the mask plate, and the elongated strip corresponds to the light-blocking portion of the mask plate. If negative photoresist is used, the positions corresponding to the light-transmitting portion and the light-blocking portion are reversed.
By taking positive photoresist as an example, an exposure process is performed on the second transparent electrode through a mask plate which has a configuration as shown in FIG. 1 and comprises elongated strips 11 and slits 12. The second transparent electrode is formed with a configuration as shown in FIG. 1 after other patterning processes, which comprises elongated strips with a width of 4 μm, and slits with a width of 6 μm.
However, the inventor found that over etching or inadequate etching may appear when the second transparent electrode is patterned by a patterning process in a prior art, due to some of the following reasons: instable controlling of light-exposure quantity, instable conditions for developing, inaccurate etching time, variation in concentration of the etching liquid, etc. As a result, the width of the elongated trips of the second transparent electrode cannot maintain at around 4 μm, which will lead to an excessive off-set from a standard width of elongated strip of the second transparent electrode, so that the obtained light transmittance may not be good. Referring to FIG. 1, for instance, it shows a shape and size of an electrode pattern in an existing array substrate (which corresponds to the shape and size of an electrode pattern of the mask plate being used), wherein the electrode pattern comprises elongated strips with a width of 4 μm and slits with a width of 6 μm. Provided that over exposing occurs during exposing, too much photoresist will be removed. In this case, the transparent electrode film under no protection is etched, which leads to an over etching phenomenon, i.e., the width of the elongated strips of the second transparent electrode is smaller than 4 μm; otherwise, the width of the elongated strips is greater than 4 μm.